Pattern shape determining method, pattern shape verifying method, and pattern correcting method

ABSTRACT

According to the pattern shape determining method of the embodiment, a first reference position of a pattern shape is set on a first pattern and a second reference position of a pattern shape is set on a second pattern. Moreover, an allowable dimensional difference between the first pattern and the second pattern is set to a value corresponding to a distance from the first reference position. Then, it is determined whether the second pattern has a pattern shape identical with the first pattern, based on whether a dimensional difference between the first pattern and the second pattern is within a range of an allowable dimensional difference set at a position at which the dimensional difference is calculated.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2010-213581, filed on Sep. 24,2010; the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a pattern shapedetermining method, a pattern shape verifying method, and a patterncorrecting method.

BACKGROUND

Recent progress of a semiconductor manufacturing technology is extremelyremarkable, and semiconductor devices with a minimum feature size of 40nm are mass-produced. Such scaling of semiconductor devices is realizedby rapid progress of a micro-patterning technology such as a maskprocess technology, a photolithography technology, and an etchingtechnology. In the generation in which a pattern size is sufficientlylarge, a plane shape of an integrated circuit pattern that needs to beformed on a wafer is directly written as a design pattern and a maskpattern faithful to the design pattern is manufactured. Then, themanufactured mask pattern is transferred onto the wafer by projectionoptics, and a pattern approximately the same as the design pattern isformed on the wafer by etching a base with resist as a processing targetfilm.

However, with the progress of scaling of an integrated circuit pattern,it has become difficult to faithfully form a pattern in each process.Consequently, a problem arises in that final finished dimensions do notbecome as a design pattern. Specially, in the lithography process or theetching process that is the most important process for achievingmicro-patterning, patterns arranged around a pattern that needs to beformed greatly affect the dimensional accuracy of the pattern that needsto be formed.

In order to avoid such influence, technologies, such as the OPC (OpticalProximity Correction) and the PPC (Process Proximity Correction), aredeveloped. In these technologies, an auxiliary pattern is added inadvance or a width of a pattern is thickened or thinned so that a shapeof a processed integrated circuit pattern becomes a design pattern(desired value).

Moreover, development of an OPC verifying technology has been progressedin which whether a pattern shape after the OPC or the PPC is appropriateis verified by OPC verification using a process simulation such aslithography and processing.

However, the OPC verification performs simulation such as lithographyand processing and therefore takes a long time in the case of beingperformed on the whole integrated circuit pattern. Therefore, identicalpatterns are extracted from the integrated circuit pattern and the samesimulation result is applied to the identical patterns. Thus, it isdesired to determine whether a pattern shape is identical betweenpatterns efficiently and accurately.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a configuration of a patternshape determining apparatus according to a present embodiment;

FIG. 2 is a flowchart illustrating a process procedure of a patternshape determining process;

FIG. 3A and FIG. 3B are diagrams for explaining determination areas;

FIG. 4 is a diagram illustrating a relationship between a pattern shapedetermination condition and an on-wafer dimensional variation amount;

FIG. 5 is a flowchart illustrating a verification process procedure whena pattern shape verifying method according to the present embodiment isapplied to a verification process of a design pattern;

FIG. 6 is a flowchart illustrating an optical-proximity-correctionprocess procedure when the pattern shape verifying method according tothe present embodiment is applied to an optical proximity correction;and

FIG. 7 is a diagram illustrating the hardware configuration of thepattern shape determining apparatus.

DETAILED DESCRIPTION

According to a pattern shape determining method of an embodiment, afirst reference position to be a determination reference position of apattern shape is set on a first pattern to be a criterion of a patternshape and a second reference position to be a determination referenceposition of a pattern shape is set on a second pattern as adetermination target for which it is determined whether a pattern shapeis identical with the first pattern. Moreover, an allowable dimensionaldifference between the first pattern and the second pattern as acriterion used when determining whether the first pattern and the secondpattern have an identical shape is set to a value corresponding to adistance from the first reference position for each distance. Then, itis determined whether the second pattern has a pattern shape identicalwith the first pattern based on whether a dimensional difference betweenthe first pattern and the second pattern calculated for each positionfrom the first reference position and the second reference position iswithin a range of an allowable dimensional difference set at a positionat which the dimensional difference is calculated.

A pattern shape determining method, a pattern shape verifying method,and a pattern correcting method according to the embodiment will beexplained below in detail with reference to the accompanying drawings.The present invention is not limited to this embodiment.

Embodiment

FIG. 1 is a block diagram illustrating a configuration of a patternshape determining apparatus according to the present embodiment. Apattern shape determining apparatus 1 is, for example, a computer thatdetermines whether a first pattern (determination reference pattern Pato be described later) to be a criterion of a pattern shape and a secondpattern (determination target pattern Pb to be described later) to be adetermination target of a pattern shape have an identical shape.

In lithography, the effect on a predetermined position (point ofinterest) on a pattern is larger in a pattern closer to the point ofinterest and is smaller in a pattern further from the point of interest.Therefore, in the present embodiment, pattern matching considering adistance from a point of interest is performed for analyzing a patternshape centered on the point of interest.

The pattern shape determining apparatus 1 in the present embodiment setsa point of interest A to be described later at a predetermined positionon a design pattern (layout data) of an integrated circuit pattern.Moreover, the pattern shape determining apparatus 1 sets an allowabledimensional difference (dimensional tolerance x to be described later)between the determination reference pattern Pa and the determinationtarget pattern Pb as a criterion value for determining whether thedetermination reference pattern Pa and the determination target patternPb have an identical shape. The pattern shape determining apparatus 1sets the dimensional tolerance x according to the distance from thepoint of interest A for each distance from the point of interest A.

The pattern shape determining apparatus 1 determines whether thedimensional difference between the determination reference pattern Paand the determination target pattern Pb is within the range of thedimensional tolerance x for each distance from the point of interest Abased on the dimensional tolerance x. The pattern shape determiningapparatus 1 determines the determination target pattern Pb determined tohave a dimensional difference within the range of the dimensionaltolerance x as a pattern having a shape identical with the determinationreference pattern Pa. Moreover, the pattern shape determining apparatus1 determines the determination target pattern Pb determined to have adimensional difference not within the range of the dimensional tolerancex as a pattern having a shape different from the determination referencepattern Pa.

The pattern shape determining apparatus 1, for example, determineswhether the determination reference pattern Pa and the determinationtarget pattern Pb have an identical shape between a first design patternand a second design pattern. Put another way, the pattern shapedetermining apparatus 1 determines whether the determination referencepattern Pa included in the first design pattern and the determinationtarget pattern Pb included in the second design pattern have anidentical shape.

The pattern shape determining apparatus 1 can determine whether thedetermination reference pattern Pa and the determination target patternPb have an identical shape in one design pattern such as for one chip orone shot. Moreover, the pattern shape determining apparatus 1 can set apattern near a hot spot as the determination reference pattern Pa.

The hot spot is a portion in which dimensional variation is large in apattern formed on a substrate such as a wafer and is a position(coordinates) having a possibility to be a pattern formation failurehigher than a predetermined value. In other words, the hot spot is aportion that causes a problem (such as disconnection and short-circuitof a pattern) on a wafer detected in a lithography simulation or thelike.

The pattern shape determining apparatus 1 includes an input unit 11, apoint-of-interest setting unit 12, a determination area setting unit 13,an allowable-dimensional-difference setting unit 14, adetermination-reference-position setting unit 15, a shape comparing unit16, a pattern classifying unit 17, and an output unit 18.

The first design pattern (for example, for one chip or one shot) inwhich the point of interest A and the determination reference pattern Paare set, the second design pattern (for example, for one chip or oneshot) in which the determination target pattern Pb is set, and the likeare input to the input unit 11. The input unit 11 sends the first designpattern to the point-of-interest setting unit 12 and sends the seconddesign pattern to the determination-reference-position setting unit 15.

The point-of-interest setting unit 12 sets the point of interest A onthe first design pattern. The point-of-interest setting unit 12, forexample, sets respective positions on the first design pattern to thepoint of interest A in order with predetermined dimensional intervals.The point-of-interest setting unit 12 can set the position of a minimumdimension on the first design pattern, the hot spot, the positionspecified by an engineer based on past findings or the like, or the liketo the point of interest A. The point-of-interest setting unit 12 sendsthe coordinates of the point of interest A and the first design patternto the determination area setting unit 13.

The determination-reference-position setting unit 15 sets the referenceposition (determination target reference position B) of thedetermination target pattern Pb on the second design pattern. Thedetermination-reference-position setting unit 15 sets respectivepositions on the second design pattern to the determination targetreference position B in order with predetermined dimensional intervals.The determination-reference-position setting unit 15 sends thecoordinates of the determination target reference position B and thesecond design pattern to the determination area setting unit 13.

The determination area setting unit 13 sets an area (determination areaJa) to be a determination reference (determination target) of a patternshape around the point of interest A. The determination area Ja is, forexample, an area having a predetermined distance range from the point ofinterest A on the first design pattern. The determination area settingunit 13 sets one to a plurality of the determination areas Ja on thefirst design pattern, for example, by setting a distance range in a plusX direction, a distance range in a minus X direction, a distance rangein a plus Y direction, and a distance range in a minus Y direction fromthe point of interest A.

Moreover, the determination area setting unit 13 sets an area(determination area Jb) to be a determination target of a pattern shapearound the determination target reference position B. The determinationarea Jb is, for example, an area having a predetermined distance rangefrom the determination target reference position B on the second designpattern. The determination area Ja and the determination area Jb areareas having the same size.

For example, the center coordinates (coordinates of the point ofinterest A in the determination area Ja) of the determination area Jaand the center coordinates (coordinates of the determination targetreference position B in the determination area Jb) of the determinationarea Jb are the same coordinates. The determination area setting unit 13associates the determination area Ja and the determination area Jb thatare set as areas having the same size with each other and generatesinformation (information indicating a set of the determination areas Jaand Jb associated for each size of an area) indicating the association,and sends the information to the allowable-dimensional-differencesetting unit 14.

The determination area setting unit 13 sends the coordinates (ranges) ofthe determination areas Ja on the first design pattern and the firstdesign pattern to the allowable-dimensional-difference setting unit 14.Moreover, the determination area setting unit 13 sends the coordinates(ranges) of the determination areas Jb on the second design pattern andthe second design pattern to the allowable-dimensional-differencesetting unit 14.

The allowable-dimensional-difference setting unit 14 sets thedimensional tolerance x between the determination reference pattern Paand the determination target pattern Pb for each set of thedetermination areas Ja and Jb. The dimensional tolerance x is acriterion for determining whether the determination reference pattern Paand the determination target pattern Pb have an identical shape. Theallowable-dimensional-difference setting unit 14 sets the dimensionaltolerance x for each set of the determination areas Ja and Jb based onthe distance from the point of interest A of each determination area Ja.Consequently, the dimensional tolerance x according to the distance fromthe point of interest A is set for each set of the determination areasJa and Jb.

The allowable-dimensional-difference setting unit 14 sets thedimensional tolerance x, for example, based on the dimensional tolerance(reference value for determining whether or not the determination areasJa and Jb have an identical shape) between on-wafer pattern dimensionswhen the determination reference pattern Pa is formed on a wafer andon-wafer pattern dimensions when the determination target pattern Pb isformed on a wafer. The allowable-dimensional-difference setting unit 14can set the dimensional tolerance x based on minimum pattern dimensionsin the determination target pattern Pb. The dimensional tolerance x isset to, for example, a dimension that is 5% or less of the minimumpattern dimensions of the determination reference pattern Pa or thedetermination target pattern Pb. The allowable-dimensional-differencesetting unit 14 sends a set of the set dimensional tolerance x, thedetermination area Ja, and the determination area Jb to the shapecomparing unit 16.

The shape comparing unit 16 determines whether the determinationreference pattern Pa and the determination target pattern Pb have anidentical shape based on the dimensional tolerance x for each set of thedetermination areas Ja and Jb. For example, when the dimensionaldifference between the pattern dimensions of the determination referencepattern Pa in the determination area Ja and the pattern dimensions ofthe determination target pattern Pb in the determination area Jb iswithin the range of the dimensional tolerance x, the shape comparingunit 16 determines that the determination reference pattern Pa and thedetermination target pattern Pb have an identical shape. The shapecomparing unit 16 sends the result of shape determination, thedetermination reference patterns Pa, and the determination targetpatterns Pb to the pattern classifying unit 17.

The pattern classifying unit 17 associates the determination targetpatterns Pb that are each determined to have a shape identical with thedetermination reference pattern Pa among the determination targetpatterns Pb with each other, as an identical shape group. Moreover, thepattern classifying unit 17 associates the determination targetpatterns-Pb that are each determined to have a shape different from thedetermination reference pattern Pa among the determination targetpatterns Pb with each other, as a non-identical shape group. The patternclassifying unit 17 sends the determination target patterns Pb set inthe identical shape group and the determination target patterns Pb setin the non-identical shape group to the output unit 18.

The output unit 18 sends each of the determination target patterns Pbset in the identical shape group and the determination target patternsPb set in the non-identical shape group to a pattern shape verifyingapparatus 2 or a pattern correcting apparatus 3.

The pattern shape verifying apparatus 2 is an apparatus that derives theshape of an on-wafer pattern (resist pattern or etched pattern), forexample, by applying the OPC and the lithography simulation to thesecond design pattern. The OPC to the second design pattern can beperformed by the pattern correcting apparatus 3. The pattern shapeverifying apparatus 2 sets an identical on-wafer pattern (for example,on-wafer pattern of the determination reference pattern Pa) with respectto the determination target pattern Pb set in the identical shape group.The pattern shape verifying apparatus 2 verifies the derived shape ofthe on-wafer pattern by comparing the shape of the on-wafer pattern withthe second design pattern. The pattern shape verifying apparatus 2 sendsthe shape verification result of the on-wafer pattern to the patterncorrecting apparatus 3.

The pattern correcting apparatus 3 generates a mask pattern (correctionpattern) by performing the OPC on the second design pattern based on theshape verification result of the on-wafer pattern. The patterncorrecting apparatus 3 applies an identical mask pattern to thedetermination target pattern Pb set in the identical shape group. Thepattern correcting apparatus 3 can correct a mask-pattern based on thedetermination target patterns Pb set in the identical shape group andthe determination target patterns Pb set in the non-identical shapegroup. In this case, the pattern correcting apparatus 3 corrects a maskpattern by using a correction pattern library to be described later.

Next, the process procedure of the pattern shape determining process isexplained. FIG. 2 is a flowchart illustrating the process procedure ofthe pattern shape determining process. The first design pattern in whichthe determination reference patterns Pa are set, the second designpattern in which the determination target patterns Pb are set, and thelike are input to the input unit 11 of the pattern shape determiningapparatus 1. The input unit 11 sends the first design pattern to thepoint-of-interest setting unit 12 and sends the second design pattern tothe determination-reference-position setting unit 15.

The point-of-interest setting unit 12 sets the point of interest A onthe first design pattern (Step S10). The point-of-interest setting unit12, for example, sets the hot spot on the first design pattern as thepoint of interest A. The point-of-interest setting unit 12 sends thecoordinates of the point of interest A and the first design pattern tothe determination area setting unit 13.

Moreover, the determination-reference-position setting unit 15 sets thedetermination target reference position B on the second design pattern(Step S20). The determination-reference-position setting unit 15 setsrespective positions on the second design pattern to the determinationtarget reference position B in order with predetermined dimensionalintervals. The determination-reference-position setting unit 15 sendsthe coordinates of the determination target reference position B and thesecond design pattern to the determination area setting unit 13.

The determination area setting unit 13 sets one to a plurality of thedetermination areas Ja to be determination reference of a pattern shapearound the point of interest A. Moreover, the determination area settingunit 13 sets the determination areas Jb to be determination targets of apattern shape around the determination target reference position B. Thedetermination area setting unit 13 sets the determination area Jb havingthe same size as the determination area Ja with respect to the point ofinterest A.

The determination areas Ja and Jb are explained. Because thedetermination area Ja and the determination area Jb are similar areas,only the determination area Ja is explained. FIG. 3A and FIG. 3B arediagrams for explaining the determination areas. FIG. 3A illustrates atop view of a first design pattern 50 and FIG. 3B illustrates a top viewof the determination area Ja.

As shown in FIG. 3A, the point of interest A is set to a position on thefirst design pattern 50. As shown in FIG. 3B, the determination areasetting unit 13 sets a determination area 51 a, a determination area 52a, a determination area 53 a, and the like as the determination areas Jaaround the point of interest A. For example, the determination area 51 ais a square area centered on the point of interest A. The determinationarea 52 a is a ring-shaped area surrounding the perimeter of thedetermination area 51 a, and the outer perimeter of the determinationarea 52 a forms a square. The determination area 53 a is a ring-shapedarea surrounding the perimeter of the determination area 52 a, and theouter perimeter of the determination area 53 a forms a square.

The determination area 51 a is, for example, a square area (range of 75nm in vertical and horizontal directions from the point of interest A)having a width of 150 nm in an x-axis direction and a Y-axis direction.The determination area 52 a is, for example, an area obtained by cuttingout the determination area 51 a from a square area (range of 350 nm invertical and horizontal directions from the point of interest A) havinga width of 700 nm in the x-axis direction and the Y-axis direction. Thedetermination area 53 a is, for example, an area obtained by cutting outthe determination areas 51 a and 52 a from a square area (range of 2500nm in vertical and horizontal directions from the point of interest A)having a width of 5 μm in the x-axis direction and the Y-axis direction.

The determination area setting unit 13 sets determination areas 51 b to53 b (not shown) as the determination areas Jb having the same sizes asthe determination areas 51 a to 53 a on the second design pattern. Thedetermination area setting unit 13 associates the determination area 51a and the determination area 51 b that are set as areas having the samesize with each other. In the similar manner, the determination areasetting unit 13 associates the determination area 52 a and thedetermination area 52 b with each other and associates the determinationarea 53 a and the determination area 53 b with each other. Thedetermination area setting unit 13 generates information indicating eachof the associations of the determination areas 51 a and 51 b, thedetermination areas 52 a and 52 b, and the determination areas 53 a and53 b and sends the information to the allowable-dimensional-differencesetting unit 14.

A plurality of sets of the determination areas 51 a to 53 a is set onthe first design pattern 50 and a plurality of sets of the determinationareas 51 b to 53 b is set on the second design pattern. It is applicablethat each set of the determination areas 51 a to 53 a set on the firstdesign pattern 50 overlaps an adjacent different set of thedetermination areas 51 a to 53 a in part of the areas. In the similarmanner, it is applicable that each set of the determination areas 51 bto 53 b set on the second design pattern overlaps an adjacent differentset of the determination areas 51 b to 53 b in part of the areas.

The determination area setting unit 13 sends the coordinates of thedetermination areas 51 a to 53 a on the first design pattern 50 and thefirst design pattern 50 to the allowable-dimensional-difference settingunit 14. Moreover, the determination area setting unit 13 sends thecoordinates of the determination areas 51 b to 53 b on the second designpattern and the second design pattern to theallowable-dimensional-difference setting unit 14.

The allowable-dimensional-difference setting unit 14 sets thedimensional tolerances x corresponding to the distance from the point ofinterest A (Step S30). Specifically, theallowable-dimensional-difference setting unit 14 sets the dimensionaltolerance x between the determination reference pattern Pa and thedetermination target pattern Pb for each set of the determination areasJa and Jb. In other words, the dimensional tolerance x is associatedwith each set of the determination areas Ja and Jb. The dimensionaltolerances x corresponding to the distance from the point of interest Acan be derived in advance.

For example, the allowable-dimensional-difference setting unit 14 setsthe dimensional tolerance x to zero (no tolerance) with respect to a setof the determination areas 51 a and 51 b. Moreover, theallowable-dimensional-difference setting unit 14, for example, sets thedimensional tolerance x to 1 nm with respect to a set of thedetermination areas 52 a and 52 b and sets the dimensional tolerance xto 5 nm with respect to a set of the determination areas 53 a and 53 b.The allowable-dimensional-difference setting unit 14 sends a set of theset dimensional tolerance x and the determination areas Ja and Jb to theshape comparing unit 16.

The shape comparing unit 16 compares the pattern shapes of thedetermination reference pattern Pa and the determination target patternPb based on the dimensional tolerance x for each set of thedetermination areas Ja and Jb (Step S40). At this time, the shapecomparing unit 16 determines whether each of the dimensional differencesbetween the pattern dimensions of the determination reference patternsPa at the first to the N-th (N is a natural number) coordinates in thedetermination area Ja and the pattern dimensions of the determinationtarget patterns Pb at the first to the N-th coordinates in thedetermination area Jb is within the dimensional tolerance x (within theallowable range). Based on this determination result, the shapecomparing unit 16 determines whether the determination reference patternPa and the determination target pattern Pb have an identical shape foreach set of the determination areas 51 a and 51 b to the determinationareas 53 a and 53 b.

For example, when the dimensional difference at the same coordinatesbetween the pattern dimensions of the determination reference pattern Pain the determination area 51 a and the pattern dimensions of thedetermination target pattern Pb in the determination area 51 b is zero(same dimensions), the determination reference pattern Pa and thedetermination target pattern Pb are determined to have an identicalshape in the determination areas 51 a and 51 b.

In the similar manner, when the dimensional difference at the samecoordinates between the pattern dimensions of the determinationreference pattern Pa in the determination area 52 a and the patterndimensions of the determination target pattern Pb in the determinationarea 52 b is 1 nm or less, the determination reference pattern Pa andthe determination target pattern Pb are determined to have an identicalshape in the determination areas 52 a and 52 b.

Moreover, when the dimensional difference at the same coordinatesbetween the pattern dimensions of the determination reference pattern Pain the determination area 53 a and the pattern dimensions of thedetermination target pattern Pb in the determination area 53 b is 5 nmor less, the determination reference-pattern Pa and the determinationtarget pattern Pb are determined to have an identical shape in thedetermination areas 53 a and 53 b. The shape comparing unit 16 sends theresult of the shape determination, the determination reference patternsPa, and the determination target patterns Pb to the pattern classifyingunit 17.

When the shape comparing unit 16 determines that the dimensionaldifference between the pattern dimensions of the determination referencepattern Pa and the pattern dimensions of the determination targetpattern Pb is within the allowable range (Yes at Step S50), the patternclassifying unit 17 sets the determination target pattern Pb determinedto have a dimensional difference within the allowable range in theidentical shape group (Step S60).

On the other hand, when the shape comparing unit 16 determines that thedimensional difference between the pattern dimensions of thedetermination reference pattern Pa and the pattern dimensions of thedetermination target pattern Pb is not within the allowable range (No atStep S50), the pattern classifying unit 17 sets the determination targetpattern Pb determined to have a dimensional difference not within theallowable range in the non-identical shape group (Step S70).

The pattern classifying unit 17 sends the determination target patternsPb set in the identical shape group, the determination target patternsPb set in the non-identical shape group, and the determination referencepatterns Pa to the output unit 18. The output unit 18 sends each of thedetermination target patterns Pb set in the identical shape group, thedetermination target patterns Pb set in the non-identical shape group,and the determination reference patterns Pa to the pattern shapeverifying apparatus 2 or the pattern correcting apparatus 3.

Thereafter, the pattern shape verifying apparatus 2 verifies the shapeof an on-wafer pattern based on the second design pattern. At this time,the pattern shape verifying apparatus 2 applies an identical on-waferpattern to the determination target pattern Pb set in the identicalshape group to omit a shape deriving process for overlapping on-waferpatterns. The pattern shape verifying apparatus 2 sends the verificationresult to the pattern correcting apparatus 3.

Then, the pattern correcting apparatus 3 corrects the second designpattern based on the shape verification result of on-wafer patterns. Atthis time, the pattern correcting apparatus 3 applies an identicalcorrection pattern to the determination target pattern Pb set in theidentical shape group to omit a calculation process for overlappingcorrection patterns.

Next, explanation is made for a maximum variation amount (hereinafter,on-wafer dimensional variation amount) of on-wafer dimensions from theideal value in the case where the pattern shape determining apparatus 1determines that the determination reference pattern Pa and thedetermination target pattern Pb have an identical shape. FIG. 4 is adiagram illustrating a relationship between a pattern shapedetermination condition and the on-wafer dimensional variation amount.In FIG. 4, a horizontal axis indicates a distance from the point ofinterest A and a vertical axis indicates the dimensional tolerance x.

A variation amount area 60 of the on-wafer dimensional variation amountis an area in which a deviation amount of on-wafer dimensions from theideal value is 0 to 1 nm. In the similar manner, the variation amountareas 61 to 65 are areas in which a deviation amount of on-waferdimensions from the ideal value is 1 nm to 2 nm, 2 nm to 3 nm, 3 nm to 4nm, 4 nm to 5 nm, and 5 nm to 6 nm, respectively. Moreover, thevariation amount areas 66 to 70 are areas in which a deviation amount ofon-wafer dimensions from the ideal value is 6 nm to 7 nm, 7 nm to 8 nm,8 nm to 9 nm, 9 nm to 10 nm, and 10 nm to 11 nm, respectively.

In this example, when the dimensional tolerance x from the determinationreference pattern Pa in the determination area 51 a set around the pointof interest A is zero (perfect matching of patterns), the pattern shapesare determined to be identical. Moreover, it is determined whether thepattern shapes are identical while changing the dimensional tolerance xfrom the determination reference pattern Pa arranged in thedetermination area 52 a or the like to 1 nm, 5 nm, 10 nm, and 20 nm.Furthermore, the width in the X-axis direction and the width in theY-axis direction of the determination area 52 a are changed between 50nm to 3000 nm.

In such a pattern shape determination condition, the lithographysimulation is performed on the determination target pattern Pbdetermined to have a shape identical with the determination referencepattern Pa by using the pattern shape verifying apparatus 2. In thisexample, the pattern shape verifying apparatus 2 calculates the on-waferdimensional variation amount of the determination target pattern Pbdetermined to have a shape identical with the determination referencepattern Pa.

The pattern shape verifying apparatus 2 calculates the on-waferdimensional variation amount of the determination target pattern Pb, forexample, by using an exposure condition (λ=193 nm, NA=1.20) used whentransferring the determination target pattern Pb onto a wafer.

For example, the width in the X-axis direction and the width in theY-axis direction of the determination area 52 a are set to 700 nm. Then,the dimensional tolerance x in the determination area 51 a is set tozero and the dimensional tolerance x in the determination area 52 a isset to 5 nm. In this case, as shown in FIG. 4, the on-wafer dimensionalvariation amount (effect on the point of interest A) is at most 2 nm.

In this manner, when the relationship between the pattern shapedetermination condition and the on-wafer dimensional variation amount asshown in FIG. 4 is determined in advance, derivation of the on-waferdimensional variation amount of the determination target pattern Pb andsetting of the dimensional tolerance x can be performed by using thisrelationship.

Moreover, the pattern shape verifying apparatus 2 can calculate theeffect (on-wafer dimensional variation amount) on the point of interestA by using a predetermined function. The on-wafer dimensional variationamount at the point of interest A can be calculated by using theequation (1) shown below.

$\begin{matrix}{{F\left( {X_{1},X_{2}} \right)} = {{{aX}_{1} \times \left( \frac{2 \times {J_{1}\left( X_{2} \right)}}{X_{2}} \right)^{2}} + b}} & (1)\end{matrix}$where X₁ is the dimensional tolerance x and X₂ is a distance from thepoint of interest A. Moreover, J₁ is a first order Bessel function, anda and b are coefficients calculated by using a least-squares method. Forexample, in the case of the graph shown in FIG. 4, a=1.58×10⁶ andb=1.98. F(X₁, X₂) is the on-wafer-dimensional variation amount.

For example, the dimensional tolerance x in the determination area Ja inwhich the distance from the point of interest A in vertical andhorizontal directions is 150 nm is set to zero. Moreover, thedimensional tolerance x in the determination area Ja in which thedistance from the point of interest A in vertical and horizontaldirections is 150 nm to 700 nm is set to 1 nm and the dimensionaltolerance x in the determination area Ja in which the distance from thepoint of interest A in vertical and horizontal directions is 700 nm isset to 5 nm. In this case, when the on-wafer dimensional variationamount is calculated by performing the lithography simulation on thedetermination target pattern Pb determined to have a shape identicalwith the determination reference pattern Pa, it is found that theon-wafer dimensional variation amount at the point of interest A is lessthan 2 nm.

Next, explanation is made for the difference between the determinationresult when pattern determination is performed by the pattern shapedetermining method according to the present embodiment and thedetermination result when pattern determination is performed by using adifferent method. Determination of a pattern shape is performed byvarious methods (1) to (3) with respect to 31 design patterns that arefound in advance that the on-wafer-dimensional variation amount at thepoint of interest A is 2 nm or less.

Method (1)

When pattern shapes are determined to be identical in the case wherepattern shapes in shape determination images of the design patternsperfectly match, it is determined that there are seven patternvariations (seven pattern shapes) in the 31 design patterns.

Method (2)

When pattern shapes are determined to be identical in the case wherepattern shapes in shape determination images of the design patterns havea dimensional difference of 1 nm or less or less than 1 nm, it isdetermined that there are four pattern variations in the 31 designpatterns.

Method (3)

When determination of a pattern shape is performed by the pattern shapedetermining method according to the present embodiment, it is determinedthat there is only one pattern variation (all of patterns have anidentical shape) in the 31 design patterns. In this manner, whendetermination of a pattern shape is performed while considering theeffect on the point of interest A, 31 patterns are verified by verifyingone pattern shape as representative, so that the time for patternverification can be reduced significantly.

Next, explanation is made for the verification process procedure whenthe pattern shape determining method according to the present embodimentis applied to the verification process of a design pattern. FIG. 5 is aflowchart illustrating the verification process procedure when thepattern shape verifying method according to the present embodiment isapplied to the verification process of a design pattern. The seconddesign pattern (GDS data), which is a determination target for a patternshape and a verification target for a pattern shape, is input to thepattern shape verifying apparatus 2.

The pattern shape verifying apparatus 2 is connected to a hot spotlibrary 31 in which various hot spots are stored. The hot spot library31 is a storing unit, such as database, that stores findings (patternshape including a hot spot) found from a lithography simulation, aprocess simulation, a result of an actually-formed on-wafer pattern, andthe like. The hot spot is a pattern having a possibility to be a patternformation failure higher than a predetermined value when beingpattern-transferred onto a wafer.

The hot spots are input to the pattern shape verifying apparatus 2 fromthe hot spot library 31. The pattern shape verifying apparatus 2extracts patterns having the same pattern shape as the hot spots fromthe second design pattern. Specifically, shape comparison (patternmatching) of the determination reference pattern Pa and thedetermination target pattern Pb is performed with the hot spot as thedetermination reference pattern Pa (Step S110). In other words, thepoint of interest A is set on a pattern including the hot spot and thedetermination target reference position B is set on the second designpattern. Then, shape comparison of the determination reference patternPa and the determination target pattern Pb is performed centered on thepoint of interest A and the determination target reference position B.The pattern shape verifying apparatus 2 extracts an area that does notmatch the hot spot from the second design pattern (Step S120).

The pattern shape verifying apparatus 2 is connected to a clean patternlibrary 32 that stores various clean patterns. The clean pattern library32 is a storing unit, such as database, that stores findings (patternshape including a clean pattern) found from a lithography simulation, aprocess simulation, a result of an actually-formed on-wafer pattern, andthe like. The clean pattern is a pattern that is found not to become thehot spot and is a pattern that does not need pattern verification. Inother words, the clean pattern is a pattern having a possibility to be apattern formation failure lower than a predetermined value when beingpattern-transferred onto a wafer. The clean patterns are input to thepattern shape verifying apparatus 2 from the clean pattern library 32.

The pattern shape verifying apparatus 2 extracts patterns having thesame pattern shape as the clean patterns from the second design pattern.Specifically, shape comparison (pattern matching) of the determinationreference pattern Pa and the determination target pattern Pb isperformed with the clean pattern as the determination reference patternPa (Step S130). In other words, the point of interest A is set on apattern including the clean pattern and the determination targetreference position B is set on the second design pattern. Then, shapecomparison of the determination reference pattern Pa and thedetermination target pattern Pb is performed centered on the point ofinterest A and the determination target reference position B. Thepattern shape verifying apparatus 2 extracts an area that does not matchthe clean pattern from the second design pattern (Step S140).

Consequently, an area that does not match either the hot spot or theclean pattern is extracted from the second design pattern as averification target pattern. It is applicable that the pattern shapeverifying apparatus 2 performs pattern matching with the clean patternfirst and thereafter performs pattern matching with the hot spot.

In terms of a pattern finally remained as the verification targetpattern, an on-wafer pattern and the like are unknown. Therefore, thelithography simulation and the like are performed on the verificationtarget pattern and the presence or absence of a problematic portion(pattern that needs to be corrected) and the like are analyzed.

Specifically, the pattern shape verifying apparatus 2 performs the OPCon the verification target pattern and performs the lithographysimulation on the verification target pattern after the OPC, therebyderiving the shape of an on-wafer pattern. The pattern shape verifyingapparatus 2 verifies the derived shape of the on-wafer pattern bycomparing the shape of the on-wafer pattern with the second designpattern (Step S150). The pattern shape verifying apparatus 2 sends theshape verification result of the on-wafer pattern to the patterncorrecting apparatus 3.

The pattern correcting apparatus 3 corrects the verification targetpattern based on the shape verification result of the on-wafer pattern(Step S160). Moreover, the pattern correcting apparatus 3 corrects adesign pattern of the hot spot. At this time, the pattern correctingapparatus 3 applies an identical correction pattern to the host spot setin the identical shape group to omit a calculation process foroverlapping correction patterns.

Moreover, the pattern correcting apparatus 3 corrects a design patternof the clean pattern. At this time, the pattern correcting apparatus 3applies an identical correction pattern to the clean pattern set in theidentical shape group to omit a calculation process for overlappingcorrection patterns.

In this manner, in the present embodiment, it is checked whether thesecond design pattern matches the hot spot or the clean pattern inadvance and analysis on a pattern area that matches the hot spot or theclean pattern is omitted. Therefore, a pattern area on which analysis isactually performed by simulation or the like becomes narrower than thewhole area of the second design pattern. Thus, an analysis TAT(verification TAT) can be shortened.

Moreover, the pattern shape verifying method according to the presentembodiment can be applied to the optical proximity correction (OPC) ofthe second design pattern. FIG. 6 is a flowchart illustrating anoptical-proximity-correction process procedure when the pattern shapeverifying method according to the present embodiment is applied to theoptical proximity correction. The pattern shape determining apparatus 1and the pattern correcting apparatus 3 are connected to a correctionpattern library 33 that stores various correction patterns.

The correction pattern library 33 is a storing unit, such as database,that stores the first design pattern (one to a plurality of thedetermination reference patterns Pa) for performing shape comparisonwith the second design pattern (determination target patterns Pb) and amask pattern (corrected pattern) obtained by performing the OPC on eachdetermination reference pattern Pa. In the correction pattern library33, the determination reference pattern Pa and a corrected pattern thatis the determination reference pattern Pa after correction areassociated with each other.

The determination reference patterns Pa are input from the correctionpattern library 33 to the pattern shape determining apparatus 1.Moreover, the second design pattern in which the determination targetpatterns Pb are set and the like are input to the pattern shapedetermining apparatus 1.

The pattern shape determining apparatus 1 performs shape comparison(pattern matching) of the determination reference pattern Pa and thedetermination target pattern Pb (Step S210). The pattern shapedetermining apparatus 1 extracts the determination target pattern Pbthat matches the determination reference pattern Pa in shape from thesecond design pattern based on the result of the pattern matching.

The pattern shape determining apparatus 1 sends the extracteddetermination target pattern Pb to the pattern correcting apparatus 3.The pattern correcting apparatus 3 reads out the corrected pattern ofthe determination reference pattern Pa corresponding to thedetermination target pattern Pb extracted by the pattern shapedetermining apparatus 1 from the correction pattern library 33. Thepattern correcting apparatus 3 applies the read-out corrected pattern tothe mask pattern of the determination target pattern Pb. In other words,the pattern correcting apparatus 3 replaces an area matching thedetermination reference pattern Pa with a corrected pattern (Step S220).

Furthermore, the pattern correcting apparatus 3 corrects a designpattern to a mask pattern with respect to an area that does not matchthe determination reference pattern Pa by using a rule model or a modelbase (simulation model) (Step S230). Thereafter, a mask patterncorresponding to the second design pattern is output from the patterncorrecting apparatus 3.

Consequently, an area on which correction from a design pattern to amask pattern is performed becomes narrower than the case of correctingthe whole second design pattern. Thus, a correction TAT can beshortened.

The determination process of a pattern shape is performed for example,for each layer in a wafer process. Then, a mask pattern is generated bycorrecting a design pattern and a mask (photomask) (lithography mask) ismanufactured by using the mask pattern. Moreover, a semiconductor device(semiconductor integrated circuit) is manufactured by using themanufactured mask. Specifically, exposure is performed on a wafer towhich resist is applied by using the mask, and thereafter the wafer isdeveloped to form a resist pattern on the wafer. Then, the lower layerside of the resist pattern is etched with the resist pattern as a mask.Consequently, an actual pattern is formed on the wafer. Whenmanufacturing a semiconductor device, the above-described determinationof a pattern shape, generation of a mask pattern, manufacturing of amask, exposure process, development process, etching process, and thelike are performed for each layer.

Next, the hardware configuration of the pattern shape determiningapparatus 1 is explained. FIG. 7 is a diagram illustrating the hardwareconfiguration of the pattern shape determining apparatus. The patternshape determining apparatus 1 includes a CPU (Central Processing Unit)91, a ROM (Read Only Memory) 92, a RAM (Random Access Memory) 93, adisplay unit 94, and an input unit 95. In the pattern shape determiningapparatus 1, the CPU 91, the ROM 92, the RAM 93, the display unit 94,and the input unit 95 are connected via a bus line.

The CPU 91 executes determination of a pattern by using a pattern shapedetermining program 97 that is a computer program. The display unit 94is a display apparatus such as a liquid crystal monitor, and displaysthe first design pattern, the second design pattern, the determinationareas Ja and Jb, the determination reference pattern Pa, thedetermination target pattern Pb, the point of interest A, thedetermination target reference position B, the dimensional tolerance x,the determination result of whether pattern shapes are identical, andthe like based on an instruction from the CPU 91. The input unit 95 isconfigured to include a mouse and a keyboard, and inputs instructioninformation (such as parameter necessary for determination of a patternshape) that is externally input by a user. The instruction informationinput to the input unit 95 is sent to the CPU 91.

The pattern shape determining program 97 is stored in the ROM 92 and isloaded in the RAM 93 via the bus line. FIG. 7 illustrates a state wherethe pattern shape determining program 97 is loaded in the RAM 93.

The CPU 91 executes the pattern shape determining program 97 loaded inthe RAM 93. Specifically, in the pattern shape determining apparatus 1,the CPU 91 reads out the pattern shape determining program 97 from theROM 92, loads it in a program storage area in the RAM 93, and executesvarious processes, in accordance with the input of an instruction by auser from the input unit 95. The CPU 91 temporarily stores various datagenerated in the various processes in the data storage area formed inthe RAM 93.

The pattern shape determining program 97 executed in the pattern shapedetermining apparatus 1 has a module configuration including thepoint-of-interest setting unit 12, the determination area setting unit13, the allowable-dimensional-difference setting unit 14, thedetermination-reference-position setting unit 15, the shape comparingunit 16, and the pattern classifying unit 17, which are loaded in a mainstorage device to be generated on the main storage device.

In the present embodiment, pattern verification is simplified by usingtwo libraries, i.e., the hot spot library 31 and the clean patternlibrary 32, however, pattern verification can be simplified by using anyone of the two libraries.

Moreover, in the present embodiment, it is determined whether patternshapes are identical with respect to a design pattern, however, it isapplicable to perform determination of whether pattern shapes areidentical with respect to a mask pattern.

Furthermore, the determination areas Ja and Jb are not limited to asquare area and can be an area having other shapes (for example, acircular area and a rectangular area). Moreover, the dimensionaltolerance x for each of the determination areas Ja and Jb can be set byusing the function expressed by equation (1).

Moreover, the pattern shape determining method according to the presentembodiment is not limited to light exposure of λ=193 nm and can beapplied to EUV (Extreme Ultra-Violet).

In this manner, according to the present embodiment, it is determinedwhether the determination reference pattern Pa and the determinationtarget pattern Pb have an identical shape based on the dimensionaltolerance x set according to the distance from the point of interest A,so that it becomes possible to determine whether pattern shapes areidentical between patterns efficiently and accurately.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A method of determining a pattern shape,comprising: setting, by a computer, as a point-of-interest position, afirst reference position associated with a first pattern; setting, by acomputer, as a determination reference position, a second referenceposition associated with a second pattern; setting, by a computer, aplurality of determination areas each having a predetermined range ofdistances from the first reference position to points in thedetermination area, the first pattern being located within one of thedetermination areas; setting, by a computer, allowable dimensionaldifferences for the determination areas, wherein: each of thedetermination area has a corresponding allowable dimensional difference,each of the allowable dimensional differences has a value correspondingto the predetermined range of distances of the correspondingdetermination area, and the value of the allowable dimensionaldifference for a determination area located further away from the firstreference position is larger than the value of the allowable dimensionaldifference for a determination area located closer to the firstreference position; and determining, by a computer, whether the secondpattern has a pattern shape identical with the first pattern, based onwhether a dimensional difference between a dimension of the firstpattern and a corresponding dimension of the second pattern is less thanor equal to the value of the allowable dimensional difference of thedetermination area within which the first pattern is located.
 2. Themethod according to claim 1, wherein a hot spot having a possibility tobe a pattern formation failure higher than a predetermined value whenbeing pattern-transferred onto a substrate is registered, and the firstpattern is set to the registered hot spot.
 3. The method according toclaim 1, wherein a clean pattern having a possibility to be a patternformation failure lower than a predetermined value when beingpattern-transferred onto a substrate is registered, and the firstpattern is set to the registered clean pattern.
 4. The method accordingto claim 1, wherein the allowable dimensional differences are set basedon a maximum dimensional variation amount from an ideal value at thefirst reference position of a first on-substrate pattern formed on asubstrate when the first pattern is transferred onto the substrate. 5.The method according to claim 1, wherein the allowable dimensionaldifferences are set based on a minimum pattern dimension of the secondpattern.
 6. The method according to claim 1, wherein each of the firstpattern and the second pattern is included in a design pattern.
 7. Themethod according to claim 6, wherein the first reference position is aposition of a minimum dimension on the design pattern.
 8. A method ofverifying a pattern shape, the method comprising: setting, by acomputer, as a point-of-interest position, a first reference positionassociated with a first pattern; setting, by a computer, as adetermination reference position, a second reference position associatedwith a second pattern; setting, by a computer, a plurality ofdetermination areas each having a predetermined range of distances fromthe first reference position to points in the determination area, thefirst pattern being located within one of the determination areas;setting, by a computer, allowable dimensional differences for thedetermination areas, wherein: each of the determination area has acorresponding allowable dimensional difference, each of the allowabledimensional differences has a value corresponding to the predeterminedrange of distances of the corresponding determination area, and thevalue of the allowable dimensional difference for a determination arealocated further away from the first reference position is larger thanthe value of the allowable dimensional difference for a determinationarea located closer to the first reference position; determining, by acomputer, whether the second pattern has a pattern shape identical withthe first pattern, based on whether a dimensional difference between adimension of the first pattern and a corresponding dimension of thesecond pattern is less than or equal to the value of the allowabledimensional difference of the determination area within which the firstpattern is located; calculating, by a computer, a shape of anon-substrate pattern formed on a substrate when the second pattern istransferred onto the substrate; determining, by a computer, whethercalculated on-substrate pattern has a desired shape; and calculating, bya computer, the shape of the on-substrate pattern for the second patternif the second pattern is determined not to have a patter shape identicalwith the first pattern and setting an identical on-substrate pattern forthe second pattern if the second pattern is determined to have a patternshape identical with the first pattern.
 9. The method according to claim8, wherein a hot spot having a possibility to be a pattern formationfailure higher than a predetermined value when being pattern-transferredonto a substrate is registered, and the first pattern is set to theregistered hot spot.
 10. The method according to claim 8, wherein aclean pattern having a possibility to be a pattern formation failurelower than a predetermined value when being pattern-transferred onto asubstrate is registered, and the first pattern is set to the registeredclean pattern.
 11. The method according to claim 8, wherein theallowable dimensional differences are set based on a maximum dimensionalvariation amount from an ideal value at the first reference position ofa first on-substrate pattern formed on the substrate when the firstpattern is transferred onto the substrate.
 12. The method according toclaim 8, wherein the allowable dimensional differences are set based ona minimum pattern dimension of the second pattern.
 13. The methodaccording to claim 8, wherein each of the first pattern and the secondpattern is included in a design pattern.
 14. The method according toclaim 13, wherein the first reference position is a position of aminimum dimension on the design pattern.
 15. A method of correcting apattern, the method comprising: setting, by a computer, as apoint-of-interest position, a first reference position associated with afirst pattern; setting, by a computer, as a determination referenceposition, a second reference position associated with a second pattern;setting, by a computer, a plurality of determination areas each having apredetermined range of distances from the first reference position topoints in the determination area, the first pattern being located withinone of the determination areas; setting, by a computer, allowabledimensional differences for the determination areas, wherein: each ofthe determination area has a corresponding allowable dimensionaldifference, each of the allowable dimensional differences has a valuecorresponding to the predetermined range of distances of thecorresponding determination area, and the value of the allowabledimensional difference for a determination area located further awayfrom the first reference position is larger than the value of theallowable dimensional difference for a determination area located closerto the first reference position; determining, by a computer, whether thesecond pattern has a pattern shape identical with the first pattern,based on whether a dimensional difference between a dimension of thefirst pattern and a corresponding dimension of the second pattern isless than or equal to the value of the allowable dimensional differenceof the determination area within which the first pattern is located;generating, by a computer, a mask pattern of a mask used when formingthe second patter on a substrate by correcting the second pattern; andgenerating, by a computer, the mask pattern for the second pattern ifthe second pattern is determined not to have a pattern shape identicalwith the first pattern and setting an identical mask patter for thesecond pattern if the second pattern is determined to have a patternshape identical with the first pattern.
 16. The method according toclaim 15, wherein a hot spot having a possibility to be a patternformation failure higher than a predetermined value when beingpattern-transferred onto a substrate is registered, and the firstpattern is set to the registered hot spot.
 17. The method according toclaim 15, wherein a clean pattern having a possibility to be a patternformation failure lower than a predetermined value when beingpattern-transferred onto a substrate is registered, and the firstpattern is set to the registered clean pattern.